Lithuanian Birch Log - cooking recipe

Ingredients

Cake
9 egg yolks
1 1/2 cups sugar
juice of one lemon
grated rind of two lemon
10 egg whites
1 3/4 cups flour
1 teaspoon baking powder
butter or shortening, for greasing pan
Filling
3 cups pitted prunes
1 cup sugar
1 cup butter
2 egg yolks
1 teaspoon vanilla
2 tablespoons cocoa
semisweet chocolate, melted (optional)
Frosting
2 egg whites
1 1/2 cups sugar
1/4 teaspoon cream of tartar
1/3 cup cold water
1 dash salt
1 teaspoon vanilla

Preparation

MAKE CAKE. Cream egg yolks and sugar. Add lemon juice and rind.
Beat egg whites until stiff. Add to the above mixture alternately with flour and baking powder.
Pour into a jelly-roll pan or cookie sheet lined with greased paper. (Parchment?) Bake for 15-20 minutes.
Cut off and reserve 1/3 of the cake. Place the two-thirds on a clean dish towel; spread with filling and roll up.
Roll the reserved 1/3 into 3 or 4 smaller rolls to make branches. Unequal thickness looks best. Cut one end of each little roll diagonally. Attach it to the large roll/log with icing; put at different angles. You're aiming for a tree here.
Frost the entire surface with frosting. Make birch-bark markings with either a fork and/or melted chocolate.
FILLING:.Boil the prunes. Drain; cool to room temperature Mash up finely (put thru sieve, food mill, food processor, etc.)
Ceam sugar and butter. Add egg yolks and beat well. Add prune pulp to the egg mixture, along with vanilla and cocoa.
FROSTING:.Boil some water in the lowe part of a double boiler. Keep over low flame.
Place everything except vanilla into the top part of the double boiler. Beat until well-blended. Put it over the lower part and beat constantly until the frosting forms stiff peaks. Takes about 7 minutes. Remove from heat.
Pour into a mixing bowl. Add vanilla. Beat another two minutes or until it's of spreading consistency.